Calcium-magnesium alumino-silicate (CMAS) resistant thermal barrier coatings, systems, and methods of production thereof

ABSTRACT

The thermal barrier coating includes reactive gadolinia in its microstructures and the embedded gadolinia effectively reacts with CMAS contaminant reducing the damage from CMAS. Moreover, a method to produce a CMAS resistant thermal barrier coating can include a post-treatment to the thermal barrier coating with the reactive gadolinia suspension in sol-gel state.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/101,976 filed on Jun. 6, 2016, which is a U.S. National Stageapplication of PCT/US2014/065690 filed on Nov. 14, 2014, which claimsthe benefit of and priority to U.S. Provisional Patent Application No.61/913,054 filed Dec. 6, 2013, the contents of all of which areincorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to a calcium-magnesium alumino-silicate(CMAS) resistant thermal barrier coating, an article coated with acalcium-magnesium alumino-silicate (CMAS) resistant thermal barriercoating and a method to produce the coating thereof.

BACKGROUND OF THE INVENTION

Thermal barrier coatings (TBC) are generally applied onto metallicsurfaces of, for instance, gas turbine engines or aero-space engineparts. Since such engines operate at highly elevated temperatures, thesurfaces of the metallic substrates tend to thermally expand. This maycause structural defects in engines during operation and furtheroperating failure. Thus, thermal barrier coatings are essential forthose engines in order to protect the surface from thermal stress andprevent the surface damage.

However, thermal barrier coatings often fail as a result of coatingbuckling, peeling, detaching, or even spallation during operation. Theseconditions may be caused by many factors including thermal stress andenvironmental stress.

During the operation of such aero-space substrates, thermal barriercoatings are continuously exposed to environmental contaminants, such asa dust, sand, ash, or small debris. Among those, calcium-magnesiumalumino-silicate (CMAS) contaminants cause significant damages tothermal barrier coatings. For example, at operating temperaturesexceeding 1200° C., CMAS debris melts and deposits on the surface.Occasionally, such molten CMAS penetrates the thermal barrier coatingsand then solidifies, ultimately causing spallation and destruction ofcoating.

In order to protect thermal barrier coatings from the CMAS contaminants,several methods have previously been employed. For example, anadditional protective layer has been previously applied on the surfaceof thermal barrier coating (e.g., U.S. Pat. No. 8,470,460; US. Pub. No.2013/0260132). Similarly, rare earth elements have previously been addedto the coating components for CMAS resistance (e.g., U.S. Pat. No.6,284,323; US. Pub. No. 2011/143043). The rare earth element gadoliniumis often used in thermal barrier coatings to improve CMAS resistance.Gadolinia (gadolinium oxide, Gd₂O₃) is the most commonly available formof gadolinium. Gadolinia reacts with CMAS to increase the viscosity andthe melting point of CMAS. As result, CMAS contaminants do notinfiltrate thermal barrier coatings as deeply at the operatingtemperature, reducing the amount of damage caused by CMAS in thermalbarrier coating.

However, high gadolinia content in thermal barrier coatings has causedreduction in durability and spallation resistance of thermal barriercoatings. In addition, raw gadolinia is an expensive material forconventional thermal barrier coatings. Thus, balance betweenadvantageous utilization and reasonable cost is critical for producing aCMAS resistant thermal barrier coating.

The present invention addresses the economical use of gadolinia for aCMAS resistant thermal barrier coating while maximizing durability tothe thermally and mechanically induced stresses.

SUMMARY OF THE INVENTION

The invention relates to a CMAS resistant thermal barrier coating (TBC),an article coated with a CMAS resistant thermal barrier coating, and amethod to produce such coating thereof.

In particular, the present invention provides the method to produce aCMAS resistant thermal barrier coating without applying additionalprotective layers to the conventional thermal barrier coating.

In one embodiment, this invention provides a CMAS resistant thermalbarrier coating comprising a thermal barrier coating layer and areactive gadolinia. The thermal barrier coating includesmicrostructures, such as cracks, pores, and inter-particle boundaries.The reactive gadolinia is embedded in the microstructure, or depositedon the surface of the microstructure, or deposited on the surface of thethermal barrier coating to protect the coating from CMAS contaminants.

In certain embodiments, the thermal barrier coating layer is a ceramiccoating layer comprising hafnia or fully or partially stabilizedzirconia. In particular embodiments, the stabilized zirconia caninclude, without limitation, yttria-stabilized-zirconia (YSZ),magnesia-stabilized-zirconia, calcia-stabilized-zirconia,ceria-stabilized-zirconia, or a combination thereof. In otherembodiments, the reactive gadolinia is in the form of one or morenanoparticles. The size of the gadolinia nanoparticles is notparticularly limited, but may be between about 1 nm and 500 nm indiameter, between about 5 nm and 300 nm in diameter or between about 10nm and 200 nm in diameter.

In certain embodiments, the CMAS resistant thermal barrier coating is,without limitation, between about 1 mil and 250 mil, between about 3 miland 100 mil, or between about 5 mil and 25 mil in thickness.

This invention provides an article coated with a CMAS resistant thermalbarrier coating layer, which comprises a reactive gadolinia. The articlecomprises a substrate, a thermal barrier coating and a reactivegadolinia, wherein the thermal barrier coating layer comprises amicrostructure and the reactive gadolinia is embedded in themicrostructure, or deposited on the surface of the microstructure, ordeposited on the surface of the thermal barrier coating.

In certain embodiments, the thermal barrier coating layer is a ceramiccoating layer comprising hafnia or fully or partially stabilizedzirconia. In particular embodiments, the stabilized zirconia caninclude, without limitation, yttria-stabilized-zirconia (YSZ),magnesia-stabilized-zirconia, calcia-stabilized-zirconia,ceria-stabilized-zirconia, or a combination thereof.

In other embodiments, the reactive gadolinia is in the form of one ormore nanoparticles. The size of the gadolinia nanoparticles is notparticularly limited, but may be between about 1 nm and 500 nm indiameter, between about 5 nm and 300 nm in diameter or between about 10nm and 200 nm in diameter.

In yet another embodiment, the thermal barrier coating is, withoutlimitation, between about 1 mil and 250 mil, between about 3 mil and 100mil, or between about 5 mil and 25 mil in thickness.

In still other embodiments, the article to be coated can be any articleto which a thermal barrier coating is applied. In particularembodiments, the article to be coated with the CMAS resistant thermalbarrier coating layer is, but is not limited to, a turbine fuel nozzle,a fuel nozzle guide, a combustion chamber liner, a transition duct, ablade, a vane or a blade outer air seal.

The present invention provides a method to produce a CMAS resistantthermal barrier coating. The method comprises steps of:

-   -   a) applying a thermal barrier coating layer on a substrate;    -   b) preparing a reactive gadolinia suspension; and    -   c) treating the thermal barrier coating layer with the reactive        gadolinia suspension, wherein the thermal barrier coating layer        comprises a microstructure and a reactive gadolinia is embedded        in the microstructure.

In particular embodiments, a reactive gadolinia is embedded in themicrostructure, or deposited on the surface of the microstructure, ordeposited on the surface of the thermal barrier coating. In certainembodiments, the thermal barrier coating layer is a ceramic coatinglayer comprising hafnia or fully or partially stabilized zirconia. Inparticular embodiments, the stabilized zirconia can include, withoutlimitation, yttria-stabilized-zirconia (YSZ),magnesia-stabilized-zirconia, calcia-stabilized-zirconia,ceria-stabilized-zirconia, or a combination thereof. In anotherembodiment, the thermal barrier coating layer is applied by, withoutlimitation, plasma or combustion thermal spraying, suspension plasmaspraying, or electron beam physical vapor deposition (EBPVD). In certainembodiments, the microstructure in the thermal barrier coating comprisesa ceramic matrix with at least one of cracks, pores, and inter-particleboundaries.

In yet another embodiments, the thermal barrier coating is, withoutlimitation, between about 1 mil and 250 mil, between about 3 mil and 100mil, or between about 5 mil and 25 mil in thickness.

In particular embodiments, the reactive gadolinia suspension is preparedby combining the reactive gadolinia nanoparticles with a suspensionsolvent. In certain embodiments, the suspension solvent may be anysolvent which has a viscosity of lower than 100 centipoise, lower than50 centipoise, or lower than 20 centipoise. In particular embodiments,the suspension solvent is, but is not limited to, water, acetic acid,benzene, tetrachloromethane, pentane, ethyl ether, methyl t-butyl ether,hexane, acetone, triethylamine, acetonitrile, heptane, methyl ethylketone, cyclopentane, dichloromethane, n-butyl chloride, ethyl acetate,glyme, iso-octane, methyl n-propyl ketone, tetrahydrofuran, chloroform,methyl isobutyl ketone, methanol, toluene,1,1,2-trichlorotrifluoroethane, n-butyl acetate, ethylene dichloride,chlorobenzene, methyl isoamyl ketone, xylene, n,n-dimethylformamide,trifluoroacetic acid, pyridine, cyclohexane, ethyl alcohol,o-dichlorobenzene, 1,4-dioxane, n-methylpyrrolidone, 2-methoxyethanol,dimethyl acetamide, dimethyl formamide, dimethyl sulfoxide, n-propylalcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, isopropylmyristate, petroleum ether, propylene carbonate, 1,2,4-trichlorobenzene,or a mixture thereof.

In other embodiments, the size of the gadolinia nanoparticles is notparticularly limited, but may be between about 1 nm and 500 nm indiameter, between about 5 nm and 300 nm in diameter, or between about 10nm and 200 nm in diameter. In another particular embodiment, thereactive gadolinia suspension comprises between about 1% and 90% byweight of the reactive gadolinia nanoparticles, between about 5% and 80%by weight of the reactive gadolinia nanoparticles, between about 10% and50% by weight of the reactive gadolinia nanoparticles, or between about10% and 25% by weight of the reactive gadolinia nanoparticles based onthe weight of the suspension.

In certain embodiments, the method of treating the thermal barriercoating layer comprises dipping, painting, spraying, or pressureinfiltrating with the reactive gadolinia suspension. In anotherembodiment, the method further comprises the step of removing thesuspension solvent from the treated substrate. In other certainembodiments, the method further comprises repeating the step of treatingthe thermal barrier coating layer to achieve the desired content ofgadolinia. In particular embodiments, the treating step is performedtwo, three, five, or ten times to achieve the desired content ofgadolinia.

In certain other embodiments, the article which is treated according tothe methods of the invention to produce the thermal barrier coatinglayer are further coated with an additional layer of material to providean additional property.

In particular embodiments, the article to be coated with the CMASresistant thermal barrier coating layer is, but is not limited to, aturbine fuel nozzle, a fuel nozzle guide, a combustion chamber liner, atransition duct, a blade, a vane or a blade outer air seal.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will now bedescribed in detail with reference to certain exemplary embodimentsthereof illustrated in the accompanying drawings which are given hereinbelow by way of illustration only, and thus are not limitative of thepresent invention, and wherein:

FIG. 1 is a schematic view of a CMAS resistant thermal barrier coating.

FIG. 2 shows an exemplary diagram of steps for producing a CMASresistant thermal barrier coating.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variouspreferred features illustrative of the basic principles of theinvention. The specific design features of the present invention asdisclosed herein, including, for example, specific dimensions,orientations, locations, and shapes will be determined in part by theparticular intended application and use environment.

DETAILED DESCRIPTION

The present invention provides a novel thermal barrier coating systemwhich prevents damage from CMAS environmental contaminants. The TBC ofthe present invention comprises reactive gadolinia embedded in themicrostructure, or deposited on the surface of the microstructure, ordeposited on the surface of the thermal barrier coating. The reactivegadolinia in the invention is capable of reacting with CMAS contaminantsfurther eliminating damages by CMAS contaminants.

The present invention will be more illustrated by reference to thedefinitions set forth below in the drawing and context of the followingdetailed description.

Definitions

As used herein the term “thermal barrier coating (TBC) layer” refers toa high performance coating material applied on the metallic surface ofgas turbine engine components which operate at highly elevatedtemperature. The TBC may include a single coating layer or multiplelayers. In certain embodiments, the TBC layer includes, but not is notlimited to, a ceramic coating layer which comprises hafnia or fully orpartially stabilized zirconia. In particular embodiments, the stabilizedzirconia can include, without limitation, yttria-stabilized-zirconia(YSZ), magnesia-stabilized-zirconia, calcia-stabilized-zirconia,ceria-stabilized-zirconia, or a combination thereof. In otherembodiments, the TBC layer is applied by plasma or combustion thermalspraying, suspension plasma spraying, or electron beam physical vapordeposition (EBPVD).

As used herein, “gadolinia” refers to a rare earth inorganic compoundcomprising gadolinium and oxygen. In certain embodiments, the gadoliniais a reactive material to react with CMAS debris. In other embodiments,the gadolinia is in the form of one or more nanoparticles.

As used herein the term “microstructure” refers to a minor vacantsubunit which is introduced in a coating layer as part of the standardTBC procedure or intentionally by the process of coating application. Incertain embodiments, the microstructure in the thermal barrier coatingcomprises a ceramic matrix with at least one of cracks, pores, andinter-particle boundaries.

CMAS Resistant Thermal Barrier Coatings

In one embodiment, this invention provides a CMAS resistant thermalbarrier coating comprising a thermal barrier coating layer and areactive gadolinia. In other embodiments, the microstructure in thethermal barrier coating comprises a ceramic matrix with at least one ofcracks, pores, and inter-particle boundaries. The reactive gadolinia isembedded in the microstructure, or deposited on the surface of themicrostructure, or deposited on the surface of the thermal barriercoating to protect the coating from CMAS contaminant.

The thermal barrier coating is intended to be used for controlling heattransfer and thermal stress which are transferred to the metallic base.In order to manage the heat flow efficiently, the materials for TBC mayrequire several properties, such as insulating, matching thermalexpansion coefficient or resistance to corrosion or to erosion. In suchcriteria, a ceramic material is a typically used for thermal barriercoating topcoat. In certain embodiments of the invention, the CMASresistant thermal barrier coating comprises a ceramic coating layercomprising hafnia or fully or partially stabilized zirconia. Inparticular embodiments, the stabilized zirconia can include, withoutlimitation, yttria-stabilized-zirconia (YSZ),magnesia-stabilized-zirconia, calcia-stabilized-zirconia,ceria-stabilized-zirconia, or a combination thereof.

In certain embodiments, the microstructure in the thermal barriercoating comprises a ceramic matrix with at least one of cracks, pores,and inter-particle boundaries. Such microstructures in the thermalbarrier coating may be introduced as part of the standard thermalbarrier coating procedure or intentionally by the process of coatingapplication. For example, the ceramic coating material contains porositywhich may not be avoidable during coating deposit. In another example,cracks can be introduced during the deposition, e.g., due to change oftemperature. Such microstructure is a key contributor in the presentinvention, particularly to improve CMAS resistance of the thermalbarrier coating.

In certain embodiments, the reactive gadolinia is embedded in themicrostructure, or deposited on the surface of the microstructure of thethermal barrier coating. Such reactive gadolinia may infiltrate thethermal barrier coating through the microstructures, where the gadoliniareacts with penetrating CMAS contaminants. As results, such CMAScontaminants have increased viscosity and melting point further to notcause damages by precipitating in the thermal barrier coating.

FIG. 1 depicts a schematic view of a CMAS resistant thermal barriercoating of the invention. A single thermal barrier coating layer 100 isdeposited on a substrate 130 with various microstructures, such ascracks 110 and pores 120. The microstructures in TBC layer embedparticles of reactive gadolinia in their inner spaces. The reactivegadolinia particles can be further deposited on the surface of themicrostructure, or deposited on the surface of the thermal barriercoating.

In other embodiments, the reactive gadolinia may also be deposited onthe surface of the thermal barrier coating to contact with CMAScontaminant.

In other embodiments, the reactive gadolinia is in the form of one ormore nanoparticles. In other embodiments, the size of the gadoliniananoparticles is not particularly limited, but may be between about 1 nmand 500 nm in diameter, between about 5 nm and 300 nm in diameter, orbetween about 5 nm and 200 nm in diameter.

In yet certain embodiment, the CMAS resistant thermal barrier coatingis, without limitation, between about 1 mil and 250 mil, between about 3mil and 100 mil, or between about 5 mil and 25 mil in thickness.According to the invention, the gadolinia may infiltrate entire thermalbarrier coating layer to the bottom of the layer or maybe at least a topportion from the surface. The distribution of gadolinia infiltration inthermal barrier coating layer may vary depending on total thickness ofcoating, condition of treating with the gadolinia suspension, content ofthe gadolinia suspension, size of gadolinia particle and the like. Inthis regard, the thickness of thermal barrier coating may be optimizedto effect distribution of gadolinia, physical properties of thermalbarrier coating, effectiveness for CMAS resistance, or cost of rawmaterial of gadolinia.

Gadolinia Sol Treatment

According to the present invention, the reactive gadolinia is introducedto the microstructure of the thermal barrier coating layer by gadoliniasol treatment.

In certain embodiments, the reactive gadolinia is suspended in a solventto make a reactive gadolinia suspension in sol state. In particularembodiments, the reactive gadolinia is in the form of one or morenanoparticles. The suspension is generally prepared by combining thereactive gadolinia nanoparticles with a suspension solvent. In certainembodiments, the suspension solvent, may be any solvent having aviscosity of lower than 100 centipoise, lower than 50 centipoise, orlower than 20 centipoise. In particular embodiments, the suspensionsolvent is, but is not limited to, water, acetic acid, benzene,tetrachloromethane, pentane, ethyl ether, methyl t-butyl ether, hexane,acetone, triethylamine, acetonitrile, heptane, methyl ethyl ketone,cyclopentane, dichloromethane, n-butyl chloride, ethyl acetate, glyme,iso-octane, methyl n-propyl ketone, tetrahydrofuran, chloroform, methylisobutyl ketone, methanol, toluene, 1,1,2-trichlorotrifluoroethane,n-butyl acetate, ethylene dichloride, chlorobenzene, methyl isoamylketone, xylene, n,n-dimethylformamide, trifluoroacetic acid, pyridine,cyclohexane, ethyl alcohol, o-dichlorobenzene, 1,4-dioxane,n-methylpyrrolidone, 2-methoxyethanol, dimethyl acetamide, dimethylformamide, dimethyl sulfoxide, n-propyl alcohol, isopropyl alcohol,n-butyl alcohol, isobutyl alcohol, isopropyl myristate, petroleum ether,propylene carbonate, 1,2,4-trichlorobenzene, or a mixture thereof. Thesol state suspension would be understood by one of ordinary skill in theart to have dense concentration of gadolinia nanoparticle and highviscosity.

In certain embodiments, the reactive gadolinia suspension may containbetween about 1% and 90% by weight of the reactive gadoliniananoparticles, between about 5% and 80% by weight of the reactivegadolinia nanoparticles, between about 10% and 50% by weight of thereactive gadolinia nanoparticles, or between about 10% and 25% by weightof the reactive gadolinia nanoparticles based on the weight of thesuspension. With respect of the gadolinia content, the suspension withthe highest range of gadolinia content may be in a gel state.

According to the invention, the thermal barrier coating is treated withthe gadolinia sol suspension to infiltrate the TBC with gadoliniaparticles. In certain embodiments, the method of infiltrating comprisesdipping, painting, spraying, or pressure infiltrating with the reactivegadolinia suspension. In fact, the reactive gadolinia suspensionpenetrates microstructures in the thermal barrier coating by capillaryaction and transports the gadolinia. In other certain embodiments, themethod further comprises repeating the step of treating the thermalbarrier coating layer to achieve the desired content of gadolinia. Thesuspension solution evaporates at the end of process.

In other certain embodiments, the method further comprises repeating thestep of treating the thermal barrier coating layer to achieve thedesired content of gadolinia. In particular embodiments, the treatingstep is performed two, three, five, or ten times to achieve the desiredcontent of gadolinia.

According to the invention, gadolinia sol treatment is an efficienttechnique to incorporate the reactive gadolinia to the thermal barriercoating. For instance, incorporating ratio of gadolinia particle withthe gadolinia suspension is almost 100%. To the contrast, plasma spraycoating provides only about 20% of gadolinia incorporation ratio frompowder to gadolinia incorporated in thermal barrier coating.

Method of Preparation

The present invention provides a method to produce a CMAS resistantthermal barrier coating.

In one embodiment, the method comprises steps of:

a) applying an thermal barrier coating layer on a substrate;

b) preparing a reactive gadolinia suspension; and

c) treating the thermal barrier coating layer with the reactivegadolinia suspension,

wherein the thermal barrier coating layer comprises a microstructure;and

wherein a reactive gadolinia is embedded in the microstructure, ordeposited on the surface of the microstructure, or deposited on thesurface of the thermal barrier coating. In certain embodiments, thethermal barrier coating can be a ceramic coating layer comprising hafniaor fully or partially stabilized zirconia. In particular embodiments,the stabilized zirconia can include, without limitation,yttria-stabilized-zirconia (YSZ), magnesia-stabilized-zirconia,calcia-stabilized-zirconia, ceria-stabilized-zirconia, or a combinationthereof.

In certain another embodiments, the thermal barrier coating layer isapplied by plasma or combustion thermal spraying, suspension plasmaspraying, or electron beam physical vapor deposition (EBPVD).

In certain embodiments, the microstructure in the thermal barriercoating comprises a ceramic matrix with at least one of cracks, pores,and inter-particle boundaries. Such microstructures in the thermalbarrier coating may be introduced as part of the standard thermalbarrier coating procedure or intentionally by the process of coatingapplication.

In certain embodiments, the reactive gadolinia suspension is prepared bycombining reactive gadolinia with the suspension solvent. In certainembodiments, the suspension solvent has a viscosity of lower than 100centipoise, lower than 50 centipoise, or lower than 20 centipoise. Inparticular embodiments, the suspension solvent is, but is not limitedto, water, acetic acid, benzene, tetrachloromethane, pentane, ethylether, methyl t-butyl ether, hexane, acetone, triethylamine,acetonitrile, heptane, methyl ethyl ketone, cyclopentane,dichloromethane, n-butyl chloride, ethyl acetate, glyme, iso-octane,methyl n-propyl ketone, tetrahydrofuran, chloroform, methyl isobutylketone, methanol, toluene, 1,1,2-trichlorotrifluoroethane, n-butylacetate, ethylene dichloride, chlorobenzene, methyl isoamyl ketone,xylene, n,n-dimethylformamide, trifluoroacetic acid, pyridine,cyclohexane, ethyl alcohol, o-dichlorobenzene, 1,4-dioxane,n-methylpyrrolidone, 2-methoxyethanol, dimethyl acetamide, dimethylformamide, dimethyl sulfoxide, n-propyl alcohol, isopropyl alcohol,n-butyl alcohol, isobutyl alcohol, isopropyl myristate, petroleum ether,propylene carbonate, 1,2,4-trichlorobenzene, or a mixture thereof.

In certain embodiments, the reactive gadolinia is in the form of one ormore nanoparticles. In other certain embodiments, the size of thegadolinia nanoparticles is not particularly limited, but may be betweenabout 1 nm and 500 nm, between about 5 nm and 300 nm or between about 10nm and 200 nm in diameter.

In certain embodiments, the reactive gadolinia suspension may containbetween about 1% and 90% by weight of the reactive gadoliniananoparticles, between about 5% and 80% by weight of the reactivegadolinia nanoparticles, between about 10% and 50% by weight of thereactive gadolinia nanoparticles, or between about 10% and 25% by weightof the reactive gadolinia nanoparticles based on the weight of thesuspension.

The method of infiltrating can include dipping, painting, spraying, orpressure infiltrating with the reactive gadolinia suspension. It is alsocontemplated that the method can further include evaporating thesuspension solvent.

In other certain embodiments, the method further comprises repeating thestep of treating the thermal barrier coating layer to achieve thedesired content of gadolinia. In particular embodiments, the treatingstep is performed two, three, five, or ten times to achieve the desiredcontent of gadolinia.

In another embodiments, the CMAS resistant thermal barrier coatingproduced by the method can be, without limitation, between about 1 miland 250 mil, between about 3 mil and 100 mil, or between about 5 mil and25 mil in thickness.

The disclosed methods can be advantageous to provide a CMAS resistantthermal barrier coating produced by a single treatment process. Thiseliminates further application of CMAS-protective layers and reducesprocessing time and cost.

Articles

In addition, this invention provides an article coated with a CMASresistant thermal barrier coating layer, which comprises a reactivegadolinia. The thermal barrier coating includes microstructurescomprising a ceramic matrix with at least one of cracks, pores, andinter-particle boundaries. The reactive gadolinia is embedded in themicrostructure, or deposited on the surface of the microstructure, ordeposited on the surface of the thermal barrier coating to protect thecoating from the CMAS contaminant. The article coated with a CMASresistant thermal barrier coating is particularly improved with respectto CMAS resistance.

In one embodiment, the article may comprise;

a) a substrate;

b) a thermal barrier coating layer; and

c) a reactive gadolinia;

wherein the thermal barrier coating layer comprises a microstructure;and

wherein the reactive gadolinia is embedded in the microstructure, ordeposited on the surface of the microstructure, or deposited on thesurface of the thermal barrier coating.

In certain embodiments, the article with the CMAS resistant thermalbarrier coating operates at highly elevated temperature. Such articleis, but not limited to, a turbine fuel nozzle, fuel nozzle guide,combustion chamber liner, transition duct, blade, vane or blade outerair seal.

In other embodiments, the thermal barrier coating comprises a ceramiccoating layer comprising hafnia or fully or partially stabilizedzirconia. In particular embodiments, the stabilized zirconia caninclude, without limitation, yttria-stabilized-zirconia (YSZ),magnesia-stabilized-zirconia, calcia-stabilized-zirconia,ceria-stabilized-zirconia, or a combination thereof.

In certain embodiments, the microstructure in the thermal barriercoating comprises a ceramic matrix with at least one of cracks, pores,and inter-particle boundaries. Such microstructures may be introduced aspart of the standard thermal barrier coating procedure or intentionallyby the process of coating application.

In other embodiments, the reactive gadolinia in the article is in theform of one or more nanoparticles, of which the size of the gadoliniananoparticles is not particularly limited, but may be between about 1 nmand 500 nm, between about 5 nm and 300 nm or between about 10 nm and 200nm in diameter.

In certain other embodiments, the article which is treated according tothe methods of the invention to produce the thermal barrier coatinglayer are further coated with an additional layer of material to providean additional property.

Other multilayered or segmented coating layers may be applied on theCMAS resistant thermal barrier coating of the present invention forother protective reasons. Likewise, the CMAS resistant thermal barriercoating of the present invention may be applied on the other coatinglayers for other technical improvements.

Example

FIG. 2 shows an exemplary diagram of steps for producing a CMASresistant thermal barrier coating.

A thermal barrier coating layer is applied on a blade outer air seal byelectron beam physical vapor deposition (EBPVD) under standardconditions. The thermal barrier coating is composed of a ceramic coatingmatrix comprising yttria-stabilized-zirconia (YSZ). The normal thicknessof this thermal barrier coating is about 20 mil.

A slurry gadolinia nanoparticle is prepared by mixing the gadoliniananoparticles with a 50:50 mixture by volume of water and ethanol. Theslurry suspension solution contains about 25% by weight of reactivegadolinia nanoparticles based on the total weight of the suspensionsolution. The size of the gadolinia nanoparticles in the slurrysuspension is about 10-100 nm in diameter (US Research Nanomaterials,Inc., Houston, Tex., USA).

After optionally cleaning the surface of the thermal barrier coatinglayer, the slurry gadolinia nanoparticle suspension is applied on thesurface of the thermal barrier coating layer by paint brush. Meanwhile,the elevated pressure, e.g. 10 MPa, is applied after painting with theslurry suspension for pressure infiltrating. Once the slurry suspensioninfiltrates the thermal barrier coating layer, the suspension solventevaporates at room temperature. After the solvent evaporates, the samecycle of treatment with the slurry gadolinia nanoparticle suspension isrepeated for about 10 times, until gadolinia nanoparticles incorporatesin the thermal barrier coating at least 50% of top portion from thesurface.

The invention has been described in detail with reference to preferredembodiments thereof. However, it will be appreciated by those skilled inthe art that changes may be made in these embodiments without departingfrom the principles and spirit of the invention, the scope of which isdefined in the appended claims and their equivalents.

What is claimed is:
 1. A calcium-magnesium alumino-silicate (CMAS)resistant thermal barrier coating comprising: a) a thermal barriercoating layer having a thickness; b) reactive gadolinia particles havinga diameter between 10 and 200 nanometers, wherein the thermal barriercoating comprises a microstructure and wherein the reactive gadoliniaparticles are embedded in the microstructure for at least 50% of thethermal barrier coating layer thickness from the surface of the thermalbarrier coating layer.
 2. The thermal barrier coating of claim 1,wherein the thermal barrier coating layer is a ceramic coating layercomprising hafnia or fully or partially stabilized zirconia.
 3. Thethermal barrier coating of claim 1, wherein the microstructure comprisesa ceramic matrix with at least one of cracks, pores, and inter-particleboundaries.
 4. The thermal barrier coating of claim 1, wherein thethermal barrier coating layer is applied by plasma or combustion thermalspraying, suspension plasma spraying, or electron beam physical vapordeposition (EBPVD).
 5. The thermal barrier coating of claim 1, whereinthe thermal barrier coating thickness is between 1 mil and 250 mil. 6.The thermal barrier coating of claim 1, wherein the thermal barriercoating thickness is between 5 and 25 mil.
 7. A coated articlecomprising: a) a substrate; b) a thermal barrier coating layer having athickness; and c) reactive gadolinia nanoparticles; wherein the thermalbarrier coating comprises a microstructure; and wherein the reactivegadolinia nanoparticles are embedded in the microstructure for at least50% of the thermal barrier coating layer thickness from the surface ofthe thermal barrier coating layer; and wherein the coated article is oneof a turbine fuel nozzle guide, a combustion chamber liner, a transitionduct, a blade, a vane, or blade outer air seal.
 8. The article of claim7, wherein the thermal barrier coating layer is a ceramic coating layercomprising hafnia or fully or partially stabilized zirconia.
 9. Thearticle of claim 7, wherein the microstructure comprises a ceramicmatrix with at least one of cracks, pores, and inter-particleboundaries.
 10. The article of claim 7, wherein the thermal barriercoating layer is applied by plasma or combustion thermal spraying,suspension plasma spraying, or electron beam physical vapor deposition(EBPVD).
 11. The article of claim 7, wherein the thermal barrier coatingthickness is between 1 mil and 250 mil.
 12. The article of claim 7,wherein the thermal barrier coating thickness is between 5 and 25 mil.13. A calcium-magnesium alumino-silicate (CMAS) resistant thermalbarrier coating consisting of: a) a thermal barrier coating layer havinga microstructure and a thickness; b) reactive gadolinia particles havinga diameter between 10 and 200 nanometers, and wherein the reactivegadolinia particles are embedded in the microstructure for at least 50%of the thermal barrier coating layer thickness from the surface of thethermal barrier coating layer.
 14. The thermal barrier coating of claim13, wherein the thermal barrier coating layer is a ceramic coating layerof hafnia or fully or partially stabilized zirconia.
 15. The thermalbarrier coating of claim 13, wherein the microstructure has at least oneof cracks, pores, and inter-particle boundaries.